Somali piracy has created a major externality due to disruption to shipping, especially in the Gulf of Aden. How costly is this anarchy? This column analyses micro-data on individual shipping contracts and finds that piracy increased transport costs by around 8%. The $120 million in net revenues that pirates generate are more than offset by the costs borne by the shipping industry, which lie between $0.9 billion and $3.3 billion.